eS er ae ee ae ee 
S. W. Ford—Primordial Rocks of Troy, N. Y. 33 
the whole district is covered with a thick sheet of drift, and the 
rocks bear evidence of extensive faulting, much further study 
will be necessary before it will be fully understood. 
These outcrops generally consist for the most part of coarse 
red and yellow weathering slates and shales, with occasional 
thin-bedded sandstones; but the most of them are supposed, 
and four of them are known, to hold subordinate limestone de- 
posits. Of these deposits the two western-most individually con- 
sist of a few courses of thick-bedded limestone, and of irregular, 
sometimes lenticular, sparry and frequently pebbly masses, vary- 
ing from one to several hundred pounds in weight, im ed 
in a coarse, dirty-looking arenaceous matrix; while the others 
form tolerably compact, even-bedded limestones, with an abun- 
dance of scattered black nodules, from twenty-five to thirty feet 
in thickness. 
So far as investigated, these limestones have been found to 
be highly fossiliferous, though the fossils are usually in a very 
fragmentary condition. From two of them—one of the con- 
glomerates and one of the even-bedded masses—the writer has 
made frequent collections during the last three years. Witha 
single exception the same species occur in both. Up to the 
present time they have yielded eighteen species, which are dis- 
tributed as follows: 
Protozoa (Archwocyathus) ..-~.---~---.----------- 1 species. 
Grachiopods 2. 2 ee 7 ie 
Lamellibranchiata: i222 2c 320 oe .8 1 e 
Gasteropoda......_----- oe Sine 
Pteropoda (Hyolithes)--. -- 2 zi 
Annelida ( Salterelia) 1 “ 
DeWRaiite e aes. eek eo 5 - 
Total, 18 “4 
of New York in 1848, from this locality; and two— Conoceph- 
alus (Atops) trilineatus (Emm.) and Olenellus (Olenus) asaphordes 
(H.), from Greenwich, Washington county. All the rest are new 
or undescribed.* : 
Desiring further information in regard to certain of these new 
species, I several months since wrote Mr. E. Billings, Paleon- 
tologist of the Geological Survey of Canada, at the same time 
giving him a list of the species in my possession from this 
* Unless one of them should prove identical with the species of Cypricardia 
figured by Emmons (American Geology, p. 113, plate |, fig. 1.) : 
Am. Jour. Scr.—Turp Serres, Vor. lI, No. 7.—Juzy, 1871. 
3 
